This invention relates to the catalytic allylation of hydroxyaromatic reactants. More specifically, it relates to a catalytic process for allylating hydroxyaromatic reactants in a system which is generally free of organic solvents.
U.S. Pat. No. 2,560,350 discloses the preparation of 2,2-bis(para-allyloxyphenyl)propane by reaction of an allyl halide, such as allyl chloride or allyl bromide, with 4,4'-isopropylidenediphenol, in an essentially anhydrous medium of ethanol or acetone in the presence of an HCl or HBr acceptor such as anhydrous potassium carbonate. A reaction time, at reflux temperature, of about 9 hours was reported to be necessary to complete the reaction and the product yield reported by this method was only about 49 percent. Furthermore, treatment of the resultant product mixture with an aqueous caustic solution was required to remove unreacted 4,4'-isopropylidenediphenol. This latter treatment resulted in the formation of salts which were insoluble in the reaction mixture. The formation of the salts produced an undesirable solid-liquid mixture from which the product had to be recovered and purified.
More recently, U.S. Pat. No. 3,060,243 disclosed the preparation of 2,2-bis(para-allyloxyphenyl)propane by reaction of an allyl halide with 4,4'-isopropylidenediphenol and an alkali metal hydroxide in a reaction solvent system composed of a binary mixture of water and an inert water-soluble organic solvent such as ethanol, tetrahydrofuran, acetonitrile, acetone, p-dioxane and the like. Alternatively, the patent discloses a method whereby the 4,4'-isopropylidenediphenol and the alkali metal hydroxide can be dissolved separately in the organic solvent and the water, respectively, followed by mixing the two solutions and adding the allyl halide.
It would be highly desirable to provide a method for allylating hydroxyaromatic compounds which would not require an organic solvent and which would produce the desired compounds in higher yields and at higher conversions than the methods previously described.